onExpansionWillChange property

(bool Function(bool)?) onExpansionWillChange
final

Called when the widget will change expanded state.

When the widget is going to start expanding/collapsing, this function is called with the value true/false.

Return false to prevent expanded state to change. Return true(default) to allow expanded state changing.

Implementation

final bool Function(bool)? onExpansionWillChange;